1. Technical Field
The present invention relates to a method of manufacturing an alpha-sialon phosphor and, more particularly, to a method of stabilizing alpha-sialon phosphor raw powder that prevents the deterioration of photoluminescence intensity according to humidity or the like in the raw powder treatment process.
2. Description of the Related Art
There are various methods of emitting white light from an LED system. For this purpose, typically, an LED system includes a blue LED chip and a yellow phosphor excited by the chip. Various types of LED systems have been developed since a YAG-Ce based yellow phosphor excited by a blue LED chip made of a GaN thin film was developed.
Such a yellow phosphor is a material indispensable for emitting white light because it is a material for converting near-ultraviolet light or blue light emitted from an LED chip into visible light observed with the naked eye. Currently, high-grade sensitive illuminators that can control color rendering properties and color temperature are being intensively developed by increasing the illumination efficiency of an illuminator and appropriately mixing green, yellow and red phosphors, for the purpose of the advance of white LEDs into general illumination markets. Currently, among these phosphors, an oxynitride-based phosphor, which is formed by replacing all or part of oxygen atoms of an industrially-used oxide-based phosphor with nitrogen atoms, is being intensively researched all over the world, because it exhibits excellent excitation/luminescence characteristics and high stability to temperature/humidity due to its strong covalent bonds and low electron affinity.
Meanwhile, a conventional alpha-sialon phosphor is generally synthesized by sintering a Si3N4—CaO—AlN—Eu2O3 based raw powder mixture at high temperature. However, this method is problematic in that a large amount of oxide is used, so the content of oxygen becomes high, and thus it is difficult to increase photoluminescence intensity and convert emission peak wavelengths into long wavelengths.
In order to solve the above problem, Japanese Unexamined Patent Application Publication No. 2005-307012 discloses a Ca—Eu-α-sialon, whose Ca solid solution range is wide compared to conventional α-sialon due to the use of nitride as a Ca2+ source (stabilization ion) instead of oxide, and which can easily disperse Eu2+ having a large ion radius in a solid solution.